diff --git a/keystone/limit/backends/base.py b/keystone/limit/backends/base.py
index 42188bf788..f0634106e7 100644
--- a/keystone/limit/backends/base.py
+++ b/keystone/limit/backends/base.py
@@ -166,3 +166,15 @@ class UnifiedLimitDriverBase(object):
 
         """
         raise exception.NotImplemented()  # pragma: no cover
+
+    @abc.abstractmethod
+    def delete_limits_for_project(self, project_id):
+        """Delete the existing limits which belong to the specified project.
+
+        :param project_id: the limits' project id.
+
+        :returns: a dictionary representing the deleted limits id. Used for
+            cache invalidating.
+
+        """
+        raise exception.NotImplemented()  # pragma: no cover
diff --git a/keystone/limit/backends/sql.py b/keystone/limit/backends/sql.py
index fe4700b489..afc6474453 100644
--- a/keystone/limit/backends/sql.py
+++ b/keystone/limit/backends/sql.py
@@ -348,3 +348,13 @@ class UnifiedLimit(base.UnifiedLimitDriverBase):
             ref = self._get_limit(session,
                                   limit_id)
             session.delete(ref)
+
+    def delete_limits_for_project(self, project_id):
+        limit_ids = []
+        with sql.session_for_write() as session:
+            query = session.query(LimitModel)
+            query = query.filter_by(project_id=project_id)
+            for limit in query.all():
+                limit_ids.append(limit.id)
+            query.delete()
+        return limit_ids
diff --git a/keystone/limit/core.py b/keystone/limit/core.py
index 3c2109d55e..349526fc9c 100644
--- a/keystone/limit/core.py
+++ b/keystone/limit/core.py
@@ -119,3 +119,8 @@ class Manager(manager.Manager):
     def delete_limit(self, limit_id):
         self.driver.delete_limit(limit_id)
         self.get_limit.invalidate(self, limit_id)
+
+    def delete_limits_for_project(self, project_id):
+        limit_ids = self.driver.delete_limits_for_project(project_id)
+        for limit_id in limit_ids:
+            self.get_limit.invalidate(self, limit_id)
diff --git a/keystone/resource/core.py b/keystone/resource/core.py
index e4ec7e9756..eaa6af1339 100644
--- a/keystone/resource/core.py
+++ b/keystone/resource/core.py
@@ -443,6 +443,7 @@ class Manager(manager.Manager):
             assignment.COMPUTED_ASSIGNMENTS_REGION.invalidate()
             PROVIDERS.credential_api.delete_credentials_for_project(project_id)
             PROVIDERS.trust_api.delete_trusts_for_project(project_id)
+            PROVIDERS.unified_limit_api.delete_limits_for_project(project_id)
         finally:
             # attempt to send audit event even if the cache invalidation raises
             notifications.Audit.deleted(self._PROJECT, project_id, initiator)
diff --git a/keystone/tests/unit/limit/test_backends.py b/keystone/tests/unit/limit/test_backends.py
index 78dd8d7d7f..eae88af85c 100644
--- a/keystone/tests/unit/limit/test_backends.py
+++ b/keystone/tests/unit/limit/test_backends.py
@@ -682,3 +682,27 @@ class LimitTests(object):
         self.assertRaises(exception.LimitNotFound,
                           PROVIDERS.unified_limit_api.delete_limit,
                           uuid.uuid4().hex)
+
+    def test_delete_limit_project(self):
+        # create two limits
+        limit_1 = unit.new_limit_ref(
+            project_id=self.tenant_bar['id'],
+            service_id=self.service_one['id'],
+            region_id=self.region_one['id'],
+            resource_name='volume', resource_limit=10, id=uuid.uuid4().hex)
+        limit_2 = unit.new_limit_ref(
+            project_id=self.tenant_bar['id'],
+            service_id=self.service_one['id'],
+            region_id=self.region_two['id'],
+            resource_name='snapshot', resource_limit=5, id=uuid.uuid4().hex)
+        PROVIDERS.unified_limit_api.create_limits([limit_1, limit_2])
+
+        # delete a unrelated project, the limits should still be there.
+        PROVIDERS.resource_api.delete_project(self.tenant_baz['id'])
+        ref = PROVIDERS.unified_limit_api.list_limits()
+        self.assertEqual(2, len(ref))
+
+        # delete the referenced project, the limits should be deleted as well.
+        PROVIDERS.resource_api.delete_project(self.tenant_bar['id'])
+        ref = PROVIDERS.unified_limit_api.list_limits()
+        self.assertEqual([], ref)
diff --git a/releasenotes/notes/bug-1779903-f2b22cf23a9e01f9.yaml b/releasenotes/notes/bug-1779903-f2b22cf23a9e01f9.yaml
new file mode 100644
index 0000000000..59b8eeea81
--- /dev/null
+++ b/releasenotes/notes/bug-1779903-f2b22cf23a9e01f9.yaml
@@ -0,0 +1,6 @@
+---
+features:
+  - >
+    [`bug 1779903 <https://bugs.launchpad.net/keystone/+bug/1779903>`_]
+    When a project is deleted, the limits which belong to it will be deleted
+    as well.